Roadside restaurant chain Little Chef is to close 67 of its 161 sites in a move expected to lead to the loss of between 500 and 600 jobs.

The sites earmarked for closure have been trading unprofitably for a number of years due to "a variety of economic and locational factors", the company said, but remaining sites are all trading profitably. The 500 to 600 jobs lost will be a mixture of full and part-time roles at sites across the country, and will leave a workforce of around 1,500.

Little Chef was saved by turnaround group RCapital when it fell into administration in 2007. RCapital bought the majority of the business and assets, saving 193 of the 235 restaurants and more than 3,500 jobs.

In 2008 several branches were revamped by Michelin-starred chef Heston Blumenthal as part of a Channel 4 show.

In a statement, the firm said the decision to close a number of its sites was not taken lightly, but was "essential" to allow the company to focus on developing its remaining sites, introducing the New Concept - revamping restaurants including the "Heston-treatment" - and targeting new sites.

It said the company's strategic plan was to expand its business by opening and introducing new sites over the coming years. The statement added: "Overall, Little Chef continues to trade strongly."

Little Chef chairman Graham Sims said: "When we acquired Little Chef four years ago we inherited a number of sites with leases that were uncompetitive. Despite very hard work from some very committed colleagues we have been unable to lift the performances of these sites to a level where they are viable.

"Consequently, following a thorough review in which we considered all the options, it is with regret that we have had to close a number of sites. This means some people's jobs are at risk throughout the organisation. We will do everything in our power to help every individual find alternative employment within the Little Chef organisation."

The GMB union, which has members at the chain, said the situation showed private equity was a "disaster" for jobs.

GMB senior officer Paul Maloney said: "Little Chef has shared the same history as Southern Cross and the pubcos in being financially engineered to death. Private equity has been a disaster for jobs while enriching the multi-millionaire elite."